http://blogs.msdn.com/b/directx/p/directx12.aspx
Microsoft is teasing DirectX 12. The interesting thing on there is that Snapdragon logo. From what I've remembered, DirectX has only been for Windows and has been tied to your OS. It looks like we are going to see DirectX on mobile and that by itself is a big change. Also I'm expecting it to challenge AMD's Mantle somehow.
I plan to update this thread with other announcements, so feel free to post any other GDC annoucements.